Bifunctional sulfur-doped biochar for efficient removal of tetracycline and resistant bacteria via adsorption and peroxydisulfate activation

Sulfur-doped biochar (SBC) was prepared for the efficient removal of tetracycline (TC) and TC-resistant bacteria via the dual functions of adsorption and peroxydisulfate (PDS) activation. One of the prepared SBC/PDS systems was found to remove 93.89 % of TC with 3.11 times the removal efficiency of the system without sulfur doping (i. e., BC/PDS). The SBC/PDS system inactivated approximately 10 5 CFU/mL of the TC-resistant bacterium Escherichia coli within 90 min, corresponding to 1.14 times the inactivation efficiency of the BC/PDS system. The introduction of sulfur improved the adsorption rate by 3.09 times, likely due to pore filling and hydrogen bonding. The PDS activation of the SBC/PDS system primarily removed TC and E. coli through nonradical oxidation dominated by 1 O 2 generation, and the main active sites were vacancy defects. TC adsorption may be the key step for determining the reaction rate of nonradical oxidation. A high correlation (R 2 = 0.98) was observed between the adsorption capacity and degradation rate constant of different activator systems, which indicated a synergistic effect between the adsorption and oxidation of TC. This study provides a theoretical basis for the development of advanced oxidation processes utilizing bifunctional materials with a nonradical oxidation pathway for the removal of antibiotics and antibiotic-resistant bacteria.